A market where anyone can enter tomorrow is a market where nobody earns much for long. Profits draw entrants, entrants add supply, supply pushes price down to the cost of providing the thing. That is the mechanism working properly, and the only reason any business escapes it is that entry is harder than it looks.

Barriers to entry are the things that make it harder. They are the least glamorous part of strategy and the part that determines most of the outcome.

The kinds that are real

Capital. Some businesses need a great deal of money before they earn anything. Fewer than people think, and the number falls every year, which is why capital is a weakening barrier in most of the economy and a decisive one in the parts where it still applies.

Regulation and licensing. The most durable barrier there is, because it does not decay and cannot be out-executed. It also cannot be built — you either operate in a licensed field or you do not.

Distribution. The ability to reach the customer at all. Frequently the binding constraint and almost never the one an entrant plans for, because a founder's attention is on the product. A better product with no route to the buyer loses to a worse one with a route.

Accumulated advantage. Scale, data, reputation, installed base — things that exist only because the incumbent has been doing this for years. See economies of scale and network effects; these are the same structures seen from the entrant's side.

Customer inertia. The incumbent does not have to be better, only good enough that switching is not worth the disruption. This is switching costs and it is the barrier most available to an ordinary business.

The barrier founders consistently misidentify

Ask an owner what stops competitors and they will usually name the skill. The technical difficulty, the judgment, the years it took to get good.

It is almost never the skill. Skill is the barrier that was hardest for them, which is a fact about their history and not about the market. Someone else who already has the skill faces no barrier at all, and there are more of those people than it is comfortable to assume.

The barriers that actually hold are the boring ones: the client who will not be the first to move, the certification that takes eighteen months, the supplier who will not open a second account in the region. None of them feel like an advantage because none of them were earned.

Knowing which way they point

Barriers protect incumbents and they also imprison them. The same regulation that keeps competitors out keeps you in a market that may be shrinking. Capital committed to a plant is capital that cannot leave when demand moves. High barriers in both directions are what produce industries where everyone is unhappy and nobody exits.

And they erode. Distribution barriers have collapsed almost everywhere in twenty years. Capital barriers fell with cloud infrastructure. A business whose position rests on a barrier should know what maintains it, because the honest answer is often "nothing, and it has been weakening for a while" — which is the first move in commoditization.

The version of the question that is useful

Not "do we have barriers to entry", which invites a reassuring list. Instead: if a competent person with a year of runway decided to compete directly with us, what would they actually run into, in what order, and how long would each one hold them up?

The answer is usually shorter than expected. That is not a reason for despair; it is a reason to spend the current margin building one of the barriers that does hold, rather than assuming the current one is permanent.